Cooling device for vacuum apparatus



March 13, 1962 G. FRAUNHOFER ETAL 3,024,625 COOLING DEVICE FOR VACUUM APPARATUS 7 Filed June 4, 1957 INVENTORI] came F/zA owofimnunozFscilmFm United States Patent COOLING DEVICE FOR VACUUM APPARATUS Georg Fraunhofer and Rudolf 'Schliifer, Mainz, Germany,

assignors to Jenaer Glaswerk Schott & Gen., Mainz,

Germany, a German corporation Filed June 4, 1957, Ser. No. 663,513 Claims priority, application Germany June 8, 1956 5 Claims. (Cl. 62-515) The present invention relates to a cooling device for vacuum apparatus for the purpose of condensing the vapors contained within the container to be evacuated and for thus eliminating and removing them from such container.

The known cooling devices of this type usually called cooling traps when applied to vacuum apparatus each consist essentially of a condenser which is provided in the suction conduit between the vacuum pump and the container to be evacuated and is maintained at a low temperature by means of a cooling fluid. These cooling fluids usually consist, for example, of solid carbon dioxide which is dissolved in alcohol or of liquid air or oxygen. For preventing the cooling fluid from evaporating too quickly such fluid is frequently contained within a Dewar vessel.

The cooling traps provided in the suction conduit have the disadvantage of forming an additional flow resistance and of thereby considerably reducing the rate of evacuation. It has therefore already been proposed to mount the cooling traps in the container itself which is to be evacuated. However, these proposals did not lead to any satisfactory results since, due to the shape of such cooling apparatus, the efliciency thereof was very low and the apparatus also had a high consumption of cooling fluid.

It is an object of the present invention to provide a cooling apparatus which avoids the above-mentioned disadvantages of the known types of cooling traps and also possesses certain very important additional advantages.

The cooling apparatus according to the present invention is provided with a tubular coil, preferably of cylindrical shape, which is adapted to be filled with a liquid or gaseous cooling medium and is mounted within a domelike cap which is removably secured to the container to be evacuated. For many purposes, for example, when using a gaseous cooling medium, it is advisable to provide means for passing a current of such medium through the tubular coil.

Actual tests carried out by us have shown that the cooling apparatus according to our invention produced such a high rate of evacuation of the condensable gases that the high-vacuum pump, for example, a diffusion pump, had practically no other purpose left than to draw off the non-condensable gases.

On the other hand, all the known apparatus of this kind showed a very low rate of evacuation so that the length of time required for evacuating the container to a certain predetermined high vacuum depended to a large extent upon the proportion of the condensable gases within the container.

This advantage of the invention is attained by making the dimensions of the cooling surface of the tubular coil of the same order of magnitude as the dimensions of the cross-sectional area of the opening of the high-vacuum conduit.

A very high evacuation efficiency may be attained according to the invention if the tube forming the coil is made of a relatively small diameter since, at a certain area of the cooling surface, the consumption of coolant will be lower, the smaller the diameter of the coil is made. A coil of such small diameter also has the advantage that the mechanical solidity of the coil at a certain wall thickness thereof is much stronger than that of a coil of larger diameter.

Further objects, features, and advantages of the present invention will be apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawing which diagrammatically illustrates one preferred embodiment of the invention in a vertical cross section.

Referring to the drawing, a tubular coil 1 of glass and preferably made of a cylindrical shape serves as a cooling device and is mounted within a domelike cap 3. This cap 3 is removably secured to the container 2 which is to be evacuated by means of one or more pivotable clamps 4 which may be tightened or loosened by screws. A sealing ring 5 of rubber or the like is interposed between cap 3 and the mouth of container 2, and a spring ring 6 maintains rubber ring 5 in its proper position.

The two ends of coil 1 within the upper part of cap 3 terminate into containerlike extensions 7 and 8 with rounded ends into which a filling tube 9 and an exhaust tube 10 are inserted. These tubes which are made in the shape of drip tubes are tightly fused to the top wall of cap 3. Such construction, on the one hand, produces a container for holding a supply of coolant and, on the other hand, considerably reduces the evaporation of the coolant.

Although in the most preferred embodiment of the invention as shown in the drawing, coil 1 is made of a cylindrical shape, the invention is not limited to such shape but the coil may also be of any other suitable shape, for example, a plate shape which may be of advantage in many instances.

One important feature of the invention is that the adjacent coil windings abut tightly against each other. It is in many cases also of advantage if the coil projects into the container 2.

One particular embodiment of the invention tested by us consisted of a tubular coil of glass with'an inner tube diameter of 8 mm. and a wall thickness of 1 mm. The inner diameter of the cylindrical coil amounted to mm. The vessel to be evacuated had a capacity of 0.8 cubic meter.

A vacuum apparatus of such type connected to an oil diffusion pump of a normal evacuating output of 1000 liters persecond was capable, without use of the cooling device, of evacuating the vessel from a pressure of 10- to 5.10 mm. Hg within a period of two hours. If the cooling apparatus was filled with liquid oxygen, the rate of evacuation at the same difference in pressure could be reduced to 5 minutes. The consumption of coolant during the actual evacuation amounted to about liter and, when the evacuation was continued, to 1 liter per hour. The temperature of the coolant was less than -60 C.

Although our invention has been illustrated and described with reference to the preferred embodiments thereof, we wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims. 4

Having thus fully disclosed our invention, what we claim is:

1. In a vacuum apparatus comprising a container adapted to be evacuated to a low pressure, the improvement which comprises an opening of substantially smaller diameter than the diameter of the container defined through the container wall, a dome-like cap of substantially smaller size than the container removably mounted to pressure seal said opening, and a cooling coil for the passage of a cooling fluid therethrough positioned in said cap, forming an integral unit therewith whereby said cap with said coil may be removed from and attached to said container as a unit.

2. Improvement according to claim 1 in which said cap has a substantially cylindrical wall and in which said coil is a substantially cylindrically wound coil positioned adjacent said cylindrical Wall.

3. Improvement according to claim 2 in which said opening in the container is defined by a cylindrical neck of a diameter substantially corresponding to the diameter of said cap and in which said wound coil has a length sufiicient to extend into said neck.

4. Improvement according to claim 1 in which the two ends of said cooling coil have container-like enlargements thereon mounted within said cap, and including a filling tube and an exhaust tube extending through the wall of said cap and each terminating in the form of a drip tube within said enlargements.

References Cited in the file of this patent UNITED STATES PATENTS 2,283,904 Baumgarden May 26, 1942 2,431,484 Kaufman Nov. 25, 1947 2,459,329 Levinson et a1. Jan. 18, 1949 2,596,037 Maniscalco May 6, 1952 2,600,474 Brunstad June 17, 1952 2,737,030 Philipp Mar. 6, 1956 FOREIGN PATENTS 795,895 Great Britain June 4, 1958 

